let-syntax -- r7rs Definition
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Kind
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syntax;

Implemented by
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Syntax signature
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Syntax keywords:

Syntax variants:

Exports
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Exports recursive
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Description
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(let-syntax <bindings> <body>)

Syntax: <Bindings> has the form

((<keyword> <transformer-spec>) ...)

Each <keyword> is an identifier, each <transformer-spec> is an instance of syntax-rules, and <body> is a sequence of one or more definitions followed by one or more expressions. It is an error for a <keyword> to appear more than once in the list of keywords being bound.

Semantics: The <body> is expanded in the syntactic environment obtained by extending the syntactic environment of the let-syntax expression with macros whose keywords are the <keyword>s, bound to the specified transformers. Each binding of a <keyword> has <body> as its region.

(let-syntax ((given-that (syntax-rules ()
                     ((given-that test stmt1 stmt2 ...)
                      (if test
                          (begin stmt1
                                 stmt2 ...))))))
  (let ((if #t))
    (given-that if (set! if 'now))
    if))                           ===>  now

(let ((x 'outer))
  (let-syntax ((m (syntax-rules () ((m) x))))
    (let ((x 'inner))
      (m))))                       ===>  outer

The text herein was sourced and adapted as described in the "R7RS attribution of various text snippets" appendix.

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